Two of the killed and one of the wounded were female. Without any further evidence as to Rodger’s state of mind at the time, the tragedy would have been understood as just that — a tragedy — and the alleged killer assumed to have been deranged. But there were clues to his state of mind: videos of himself threatening “retribution” for his virginal sexual frustration and social loneliness, with punishment to be meted out to girls who were not attracted to him. “It’s an injustice, a crime,” he says.

Elliot Rodger spent five years planning his “Day of Retribution” during which he intended to murder his six-year-old brother who he had once apparently saved from drowning.

The “virgin killer,” who had never had a girlfriend, wrote in his manifesto that he was jealous because his younger brother had been signed up to act in television commercials.

In his manifesto, My Twisted World, Rodger wrote he had been teased by his “first crush” when he was a boy and it had “wounded me deeply.”

Monette Moio, 20, now an aspiring model, was vilified by Rodger as an “evil b–-” in the document and she is said to be distraught.

According to her father, John Moio, 75, a Hollywood stuntman, she barely recalls the killer whom she met at school when she was 10.

He said: “She doesn’t even remember this guy. She has always been the most delicate kid you would want to meet. It was just an illusion this kid built in his own mind.”

Rodger, 22, also described how he would stab in the neck his stepmother Soumaya, an actress. He intended to carry out the killings while his father, Peter Rodger, the assistant director of the Hunger Games film was away on business.

The student said he would murder his brother and stepmother a day before targeting people randomly in the university town of Isla Vista, California.

It was unclear why he altered the first part of his plan. At the time he carried it out on Friday night his father was at home, rather than away on business. Instead, Rodger stabbed to death three room-mates in his apartment, then went on a gun rampage around Isla Vista killing three more people and injuring 13 before shooting himself dead.

In the manifesto, he wrote: “I had an argument with Soumaya while I was visiting father’s house. It started when she began to boast that my brother was recently signed by an agent to act in TV commercials.

“He will become a popular kid who gets all the girls. Girls will love him. He will become one of my enemies. That was the day that I decided I would have to kill him on the Day of Retribution. I will not allow the boy to surpass me at everything, to live the life I’ve always wanted.”